Photographic fixing process and compositions



Patented Apr. 9, 1946 UNITED I STATES PATENT "oFFIcE l f 2,397,924 I PHOTO GRAPHIC FIXING PROCESS AND COMPOSITIONS.

John I. Crabtree and George T. Eaton, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N.'Y., a corporation of New Jersey No Drawing. Application October 9, 1943, Serial No. 505,530

7 Claims.

This invention relates to improved photographic procedure for the treatment of non-gelatin emulsion photographic elements and in particular to improved procedure for fixing such photographic elements. The invention also pertains to improved fixing compositions for such photographic elements. a

Various non-gelatin materials have been used 4 heretofore as protective colloids -or carriers as a acetatehave beenused-for this purpose. These substitutes are superior to gelatin in many respects but it has been noted that they frequently are not satisfactorily permeated by fixing solutions so that the removal of silver halide by conventional fixing solutions has in many cases been incomplete or required an inordinately long period of time.

This invention has for its object to provide improved procedure for the fixing of photo raphic elements bearing a non-gelatin emulsion. Another object is to provide. improved fixing compositions which permit rapid fixing of non-gelatin emulsions, and especially those which have limited-permeability to water or to the usual fixing baths. Other objects are to improve the state of the art.

These and other objects are accomplished by our invention which includes immersing a photographic element, which comprises a non-gelatin layer containing a developed silver halide photographic image, in a bath whichcontains a lower molecular weight aliphatic alcohol and a member of the group consisting of thiourea and water soluble thiocyanates as the essential fixin constituents.

nate, may be used but we prefer to use inorganic thiocyanates.

The alcohol-thiourea mixtures preferably contain between approximately 1 and 8 grams-of thiourea in 100 cc.. of water-alcohol solution. The percentage by volume of alcohol iii the water-alcohol solution may vary from 1 to 10%. The alcohol-thiocyanate mixtures preferably contain between approximately 25 and 100 grams of thiocyanate in 100 cc. of water-alcohol solution.

.The percentage by Volume of alcohol in the water-alcohol solution may vary from 1 to 70%.

When using amounts in the upper portion of the ranges given for the alcohol it is preferable to use amounts in the lower portion of the range for the other agent. Fixing baths containing the above-noted proportions of the essential fixing I constituents have been tested and in each case have been found to give a fixing time of three to three and one-half minutes or less. The exact proportions and quantities used depend upon the composition of the non-gelatin carriers which have been produced with sufilcient variation in structure to usually require fixing baths embodying all of the proportions given above. Proportions somewhat outside the ranges or amounts given can be used with satisfactory results if slower fixing times can be tolerated. In general the higher the concentration of both of the constituents the shorter will be the fixing time. Proportions in the higher ranges are not ordinarily used except for non-gelatin emulsions which are very impermeable.- The concentrations indicated give a completely clear film free of silver halide in three to three and one-half minutes. Similar tests with a conventional fixing bath containing 30% hypo required an hour for a similar degree of fixing.

The invention is applicable to non-gelatin emulsions in general and will enable shorter fixing times with all such emulsions. It is of par- In the following examples and description we ticular value in connection with those non-gelatin emulsionswhich have limited permeability to water.

What we claim is:

1. The process of fixing a photographic element, which element includes a non-gelatin layer and butyl alcohol. Examples of thiocyanates" which may be used are sodium, potassium and ammonium thiocyanate; organic thiocyanates which may be thiocyanate esters of aliphatic or aromatic organic radicals (e. g. thiocyanocatechol) or thiocyanate salts of organic'bases (e. g.

MCHahCNB) tetramethylammonium thiocyacontaining a silver image, which process comprises immersing said photographic element in a bath which contains as the essential fixing constituents a lower aliphatic alcohol and a member of the group consisting of thiourea and water soluble thiocyanates, the thiourea; when used, being present in an amount of between about 1 and 8 grams of thiourea in cc. of water-alcohol solution, the water soluble thiocyanate, when used,

the alcohol in the water alcohol solution being from about 1 to 70%.

2. The process of fixing a photographic element which includes a non-gelatinlayer containing a develope d silver image which process comprises immersing said photographic element in a bath which'contains as the essential fixing constituents between about 1 and 8 grams of thiourea in 100 cc. of a water-alcohol solution, the percentage by volume of alcohol in the wateralcohol solution being from about 1 to 70%;

3. The process of fixing a photographic ele-, ment which includes a non-gelatin layer containing'a developed silver image which process comprises immersing said photographic element in a bath'which contains as the essential fixing constituents between about 25 and 100 grams of water soluble thiocyanate in 100 cc. of water-alcohol solution, the percentage by volume of the alcohol in the water-alcohol solution being from about 1 to 70%;

4. The process of fixing aphotographic element which includes a non-gelatin layer conurea in 100 cc. of water-alcohol solution, the percentage by volume of alcoholin the water-alcohol solution being from about 1 to. 70%.v

prises immersing said photographic element in a'bath which contains as the essential fixing constituents between about 25 and 100 grams of I water soluble thiocyanate in 100 cc. of wateralcohol solution, the percentage by volume of alcohol in the water-alcohol solution being from about 1 to 70%.

taining a developed silver image and having but I limited permeability to water which process comprises immersing said photographic element in a bath which contains as the essential fixing constituents between about 1 and 8 grams of thic- 6. A fixing composition adapted to rapidly fix a photographicelement which includes 'a'nongelatin layer containing a developed silver image which composition comprises between about 1 and 8 grams of thiourea in 100 cc. of water-alcohol solution, the percentage by volume of alcohol in the water-alcohol solution being from about 1 to 70%.

7. A fixing composition, adapted to rapidly fix a photographic element which includes a nongelatin layer containing a developed silver image which composition comprises between about 25 and 100 grams of water soluble thiocyanate in 100 cc. of water-alcohol solution, the percentage by volume of alcohol in the alcohol-water solution being from about 1 to 70%.

- JOHN I. CRABTRE'E.

GEORGE T. EATON. 

